IAVCEI Commission on Tephra Hazard Modelling

HAZARD MODELS

Models for tephra dispersal are based on the mass conservation equation with different degrees of simplicity, following either Eulerian or Lagrangian formulation. The Eulerian approach describes changes in the fluid as they occur at a fixed point, whereas the Lagrangian approach describes changes which occur as following a fluid particle along its trajectory. Each approach is useful for different applications. For example, weather forecasting is based on the Eulerian approach because it is based on a fixed measurement system. Lagrangian approach is more useful when describing the evolution of a given material as it moves within a certain fluid (e.g. chemical modeling). Tephra dispersal is often described using both approaches. In particular, models commonly defined as Lagrangian are based, in fact, on an Eulerian–Lagrangian approach, which describes the dynamics of single particles within an Eulerian flow field. In contrast, Eulerian models consider the particle phase and the flow field as two different continuums. Here, we list tephra dispersal models mainly used for civil protection purposes, such as giving public and aviation warnings and planning mitigation measures.

ASH3D,  FALL3D, FLEXPART, HYSPLIT, JMA, MLDP0, MOCAGE, NAME, PUFF, HAZMAP, TEPHRA, VOL-CALPUFF

A detailed description of these models may be found at:

http://www.unige.ch/sciences/terre/mineral/CERG/Workshop/results.html.